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Drilling wheel hubs out?

Got a new set of 5 1/2" Dubro wheels that go on 1/4" axles. Drilled them to 1/4" but they're too tight. Whats the ideal next size drill up to get them right? I don't want any excess 'slop'. Thanks, Bill

RE: Drilling wheel hubs out?

Try using a prop ream in the correct size. I have found that when drilling wheels, the hole always seems to shrink just a touch after drilling. I think maybe heat build up causes it. Just drill it like you normally would, then run your prop ream through, and you will have a nice fit that does not bind or wobble.

Terry
"Old Fart" in training. (not to be an R/Cer, but to be an "Old Fart")
P-39 Brotherhood # 6
P-38 Brotherhood #69

RE: Drilling wheel hubs out?

You know, I bet a bunch of you think this is overkill but.........

Years ago I lived in a big town. There were a couple of industrial supply houses. They looked to me like big NAPA stores only they sold lathes, mills, etc, and all manner of bits and machine shop supplies etc. I was trying to make my own pistons at the time and needed accurate holes. Reamers are the answer, not drills. Those supply houses sold every size imaginable. I decided to buy a couple in sizes that would help those simple tasks, like getting accurate wheel/axle holes.

Since I've never been real happy with running a drill bit into those plastic wheels, it's almost impossible to get an accurate hole, I've been happy as a fly on a pig's lips to sit and turn that "expensive" reamer by hand.

I've not looked, but I bet there is at least one internet site for reamers, real "industrial strength" ones. Mine weren't much more expensive than the drill bits you see on the wall at Home Depot or Lowes Home Improvement.

RE: Drilling wheel hubs out?

Your right about the reamers. Anything, I believe, properly machined with a 'round' hole is reamed. I will check my prop reamer-hadn't thought about that! I did fiddle last nite on one with the sandpaper, and it is working-but man, is that tedious. Personally, I'm one who normally needs instant gratification! Guess I would need the 'F' reamer, I have a few letter drills in the box, wish I had a whole set.

RE: Drilling wheel hubs out?

The reamers Darock is talking about are sold as oversize dimentional reamers. You'll find the 1/4" range marked as .248, .249, .2495, .250 .2505 .251, .252 etc. You can find them for fractional or metric sizes. Try www.enco.com for individual pieces or whole sets.

Rule #1: Always know when to get out of Dodge.
Rule #2: Always know HOW to get out of Dodge.

RE: Drilling wheel hubs out?

ORIGINAL: TLH101
Try using a prop ream in the correct size. I have found that when drilling wheels, the hole always seems to shrink just a touch after drilling.

Most drills aren't really sharp enough to cut the plastic precisely, and even though material is indeed removed during drilling, the plastic also deforms a bit to accomodate the drill bit, resulting in a hole that is smaller than would have been made in metal.

Try drilling and tapping UHMW (Ultra High Molecular Weight) plastic some time. No matter how many times you run a tap through the threads, the threads will be very tight when trying to run in a machine screw. BTDT. Next time I need tapped holes in UHMW I'll use threaded inserts.

RE: Drilling wheel hubs out?

Well, thanks for the tips guys. Fred: you're right about drilling that plastic! I wound up using the prop reamer and rolled up sandpaper and got a nice smooth fit. The sandpaper method took a loooong time, and quite boring, but, it was do something, or watch 'Lifetime' movies with the wife. Those are some of the most boring movies ever made! They could be used for interrogating prisoners: "Talk or you watch 3 Lifetime movies in a row!"

RE: Drilling wheel hubs out?

I finally broke down and bought a set of lettered and numbered drills to add to my fractional inch drills. The extra sizes have been handy many times. They are not usually found in comsumer hardware stores - you need to get them mailorder or from an industrial supply place. Watch out for low-quality imports.

RE: Drilling wheel hubs out?

wsmalley,
I have a suggestion you may want to look at. I am not fond of the plastic wheel running on a steel axle and bearing the load of the airplane. Every one that I have ever had like that ended up wearing prematurely. I would rather drill the wheel to accept a nylon or bronze bushing. I found some nice smaller size nylon flanged bushings from SIG, and for the larger sizes, hit your LHS in the RC car section. Most of the time bushings are replaced in RC cars with bearings so they are fairly easy to get. Finding some with an ID. of 1/4" shouldn't be to hard. You may even get lucky and find some flanged bearings with that ID.

RE: Drilling wheel hubs out?

Brass bushings?

The K&S tubing is sized so that each tube size fits rather well into the next size larger. It's quite easy to use for a fixed bearing on the axle, or fixed bearing in the wheel, or both. And since drill sizes match up as well, it's easy to create an appropriate sized hole in the wheels.

The only very slight problem I ever ran into using that tubing as wheel bearings was on a CL rat racer that lived far longer than those suckers usually do. The high nitro fuel and the way it's slopped around a rat racer must have kept the wheel (only had one) wet every time we flew it. And brass is not a good metal to use around fuel. (Which is why I'm constantly amazed that most fuel tanks still are sold with brass clunks and tubing.) And one day I noticed the tire was showing grey-green stains. It still turned great, but it was obvious the brass was reacting to the fuel baths. (Have you ever opened up a really old fuel tank and looked at the brass inside?)

It also helps to put your wheels in the freezer for a little while first .. then I go up a size in bits .. I have a set of number bits and I use them .. Its not a big deal if there is a little bit of play as long as its not too much .. It will allow room for a bit off grease or oil .